Keep is an app my wife and i use quite a bit and would love to find an alternative on iOS (if there is also an Android app that would be a huge plus, our son has an Android)
I think Apple Notes may be the change we make. Everything else i am seeing is trying to incorporate google docs and a lot of other things into a sticky note app.
Go for it! It’s not as feature rich as the competitors but once you get the hang of it and have a routine it’s great. There’s also no additional cost. Others oftentimes have a premium subscription tier.
I've been using Notesnook for my daily needs right now. The app provide e2ee and can sync between device. It's available on almost every major platform.
My partner and I use Google keep as well, and finding a replacement has proven difficult. There doesn't seem to be an easy drop-in replacement.
There's Carnet, but it doesn't allow multiple people to collaborate on a note and it's not on iOS.
There's Joplin which is way more complicated than it needs to be as a Google keep replacement, and has some limited collaboration options, but no real-time collaboration.
And there's etherpad, which is web based, so you don't need any apps. It has full realtime collaboration support, and "notes" are easy and quick to spin up. The major downsides are a lacking mobile interface and that each person will have to keep track of the various etherpad links.
If anyone has a better solution, I'd love to hear it.
EDIT: I forgot about the Etherpad MyPads plugin which can be used to create a "Google drive"-esque experience with Etherpad. This would be a decent cross between Google keep, Google docs, and Google drive, but it's still not a perfect keep replacement. An example of this setup can be found here: https://mypads.domainepublic.net/?/login
Keep is also a Progressive Web App (PWA) which means you should be able to install it from your browser's menu, without needing a native app and irrespective of your phone's OS (iOS or Android).
Just go to https://keep.Google.com and then check if your browser menu has an "Install" option.